This ac voltage is switched through to the ceramic

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Unformatted text preview: bH & Co. KG • FP 1110 11. Physical fundamentals 10 2 dB/m 10 Attenuation coefficient αL 1 10 -1 a b 10 10 10 d c -2 -3 a -4 c b 10 -5 10 10 2 10 3 10 4 10 5 Hz 10 6 Frequency a) Relative air humidity 10 % b) Relative air humidity 40 % c) Relative air humidity 80 % d) Theoretic attenuation based on standard absorption: Linear attenuation is proportional to the square of the frequency of sound. Fig. 11.3.6: Dependence of attenuation coefficient on ultrasonic frequency (air temperature 20 °C) © Festo Didactic GmbH & Co. KG • FP 1110 183 11. Physical fundamentals 11.3.3 Ultrasonic proximity sensors 6 Oscillator (1) Switching status display (4) Internal constant voltage supply (7) Evaluation unit (2) Output stage with protective circuit (5) Ultrasonic transducer (8) Triggering stage (3) Switch output (6) External voltage (9) Fig. 11.3.7: Block circuit diagram of an ultrasonic proximity sensor A high frequency alternating voltage is generated to excite the piezoceramic module into...
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This note was uploaded on 11/01/2012 for the course CHEMICAL 102 taught by Professor Jamesrodriguez during the Spring '12 term at Universidad Politécnica de Cartagena.

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